I have used the command line version of GMT quite a bit but I’m still a novice with the Julia interface. This should get you started.
using GMT
theta = range(0, stop = 1.5π, length = 100)
r = abs.(0.1 * randn(100) + sin.(3 * theta))
rose([r theta.*180/π], region=[0 1.4 0 360], A=270/99, frame="xg0.2",
L="270,90,180,0", pen=(:thin, :blue), fill=:orange, fmt=:png, show=true)
